(Q1) In the second chapter of the document named "zoo.xml", find the figure(s) with caption "Tree Frogs".

document("zoo.xml")/chapter[2]//figure[caption = "Tree Frogs"]

XSLT equivalent to (Q1)

document("zoo.xml")/chapter[2]//figure[caption = "Tree Frogs"]

Actually...

<xsl:transform xsl:version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/">
    <xsl:copy-of select="document('zoo.xml')/chapter[2]//figure[caption = 'Tree Frogs']"/>
  </xsl:template>
</xsl:transform>